Sole stiffness faster? Anyone got any data?

Does anyone have any actual data on whether stiffer soles are actually faster? I don’t mean like a touring shoe compared to a Bont Vapour but how about a Specialized sub 7 vs Specialized Torch 3.0 something like that? I’m not pressing on my heel anyway so I don’t see why the stiffness of the heel to the toe of a shoe makes so much difference, thoughts?

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I can’t speak for any data, but it stands to reason that a stiffer sole would be more efficient for power transfer. Whether this efficiency difference is big enough to translate in to a measurable difference in speed is another question.

The point of clipless pedals is that, despite the small platform of the pedal itself, if the sole is stiff enough then essentially the whole sole of the shoe becomes the “platform”. This should equate to more efficient power transfer and even more comfort. If you’re pedalling with just your toes then it may be that the shoe doesn’t fit you as well as it could or your saddle is too high

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I feel like it’s all going through the ball of my foot. Just because it feels that way doesn’t make it true I know…

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Maybe it is, and maybe that could be improved.

Most of the pressure will go through there anyway because it is situated over the pedal axle and there are no doubt biomechanical reasons why this is the most common way to pedal. But that’s not to say that the rest of the foot can’t still contribute

Yes I guess you’re right. It’s strange that this is one area where there seems to be zero data. I get the theoretical ideas behind it and they all seem sound but I wonder why there’s no data. It’d be pretty easy to measure. I have old shimano r170 shoes that are fairly stiff but so un aero with the old velcro and ratchet thing but do I replace with sub 7’s or save some money and get the Torch 3.0’s… I do 1300 Watts in the sprint so stiffness is a concern. (just so you don’t think I’m trying to be fancy, my ftp sucks… !)

It is strange that most manufacturers aren’t making big claims about this like they do with claims of power savings with aero frames and wheels. No doubt it will happen at some point though.

For me, the most important thing about a shoe is that it’s comfortable. After that, performance benefits are just a bonus. This depends on your use of the shoes though. Comfort for 40 min crits is less of an issue than a 60 mile road race or an ironman. I also think a stiffer sole can often contribute to comfort as it helps eliminate the “hot spot” of the cleat under the shoe.

In other words, try both shoes and see what you think. There’s little point in buying the stiffer one if it’s uncomfortable. For what it’s worth, I have a similar sprint to you and am still rocking the shimano RO88 with a non carbon sole. And for any aero concerns, consider a pair of velotoze overshoes

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One of my takeaways from some podcasts with Josh Poertner at Silca this year is that stiffness is one of the things he had been questioning in terms of actual impact on performance. His conclusion so far is that it makes no difference, and this is from someone who specializes in looking at marginal gains.

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So, I’ve just been going through this. I had a budget of £120‐150.
Came down to Specialized Torch 2.0 with carbon sole v Northwave Sonic 2 with composite (carbon reinforced).
I previously had the Sonic 2s but the older model had a carbon sole.
Cost was neutral but in the end I went for the comfort of the Sonic 2s as they were more comfortable and this is really important to me and i cant quantify the difference in the sole.
I guess time will tell with my max power numbers - but I dont race crits so its more for personal satisfaction rather than competitive results.
In the meantime I know I’ll ride with comfort.

@awoffinden I believe GCN has done a video on frame flex and how that impacts the efficiency of riding. This would be a similar situation. A summary of their findings were that when a frame flexes that energy is not absorbed but stored in the frame that then gets transferred to the drive train when the frame unflexes. There are small amounts of energy lost to heat and vibration but very minimal. The biggest impact is in perception and responsiveness. When you put done power you want the bike to accelerate forward.

While this example was about frames and not shoes I would imagine that shoe flex would be similar. Maybe there would be additional losses as the energy that is pushed into the shoe could then push back into the riders leg rather than the pedal/crank.

I guess it’d depend on where in the pedal stroke the energy is dissipated. I assume it would push back against the foot in the lower downward quadrant where power starts reducing then because every action has equal and opposite reaction that would mean that the push back on the leg would also push against the pedal releasing the stored energy into the pedal therefore smoothing the power input.

Yep. Josh was asked this very question on the last “ask Josh Anything” podcast. Talk about chasing things down a rabbit hole!

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I was thinking about that GCN-video as well and I agree on your conclusion that the energy just gets stored momentarily.

Wait? What? They mentioned that sole stiffness in shoe soles matter in their last Q&A podcast, beginning of #5, theoretically at least. They suspect that there’s just too much noise for the signal to be experimentally measured. You are asked to think about it from a hysteresis perspective and the sole flexing back at a point in the pedal stroke where there is no recapture of the energy is a hysteric loss. I believe you’re misunderstanding here as to when/where stiffness is important and not important. This is the most important lesson to learn!

In any case, comfort>stiffness because if you’re in pain, you can’t pedal.

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If signal can’t be separated from noise maybe signal is not significant? Also the energy is possibly recaptured as I’d assume (big word assume I know…) that the energy deflects back towards the bottom of the stroke after the peak power segment where the pedals are a bit past parallel to the ground.

It’s probably because there’s a human foot involved and that part of the system can be quite variable between individuals and even with the same person. You notice the same thing when you put a real rider in the wind tunnel and the error bars exceed the measured differences of equipment. Significance depends on your goals and are for you to decide.

There’s probably no data because there’s no money in it. It isn’t necessary to prove to people that they need to spend money on a stiffer sole. Testing is expensive and there are no standards. The human foot has too many variables.

There’s not much of a recapture especially at the higher forces, eg. sprinting, when stiffness makes the most difference. There will always be a loss because hysteresis. Like the other person said, check out the silca podcast if you want to learn more.

The shoe is not just the sole, it’s the whole package. There’s a pretty big difference in build quality between the torch 3.0 and sworks 7. The sworks 7 didn’t work for me because the upper dug into my tendon. So, even though I loved the stiff sole, I couldn’t use it effectively because of the damned little piece of the upper.

Yes, I see what you mean. I actually tried on the sworks 7 the other day and also the torch 3.0. It’s the first time I’ve tried the boa dials, they’re so good! Makes my current ratchet system seem so archaic. I found the s works to be too narrow, I have a pretty wide foot but the torch shoes felt great. Just on trying to flex with my hand I couldn’t feel any stiffness difference but I guess thats nothing compared to forces from peddling. What shoes did you end up getting?

Trust that I understand the need for stiffness. I used to want a flexy shoe. Now I want them to have zero flex. Keeps the feet happy.

I rotate between the Sworks Exos and Sworks 6 now. I never felt any flex with my hands either on the bike but during the ride, you feel it. It’s a small but noticeable difference in stiffness when I went from a shimano r171 to the sworks 7. For sure there was some placebo effect as far as performance goes. It was nice having that stiff shoe and feeling that everything bit of power I was putting out was transferring down into the crank. That feeling goes away a bit once you get used it but every time you do take notice whether it’s during a sprint or climb, you realize what you get for all that extra $$.

They make the sworks 7 in a wide so maybe that would work? They’re one of the wider shoes available. I also tried the bont vapor+ and that was a shoe with the widest last I’ve ever tried. It’s too bad that shoe didn’t work out for me either because the carbon rolled up to the inside arch too high and couldn’t accommodate the way my navicular bone sticks out. Now that’s one way where a shoe being too stiff isn’t good. It would cause unrideable pain.

Interesting, I’m on the shimano R171’s which are fine but the lack of the Boa dial isn’t great. Maybe the sworks 7 wide are the way to go.

I don’t believe that a carbon soled cycling shoe performs measurably better than a fiber glass or even hard plastic soled cycyling shoe. You’re much better off selecting the more comfortable shoe in that case. Or the cheaper one.

Also, I don’t believe that a crankset with 1mm of flex at 300W performs measurably better than a crankset with 1.3mm of flex at 300W. That’s why you see cranks marketed as ‘xx% stiffer’ or ‘xxx grams lighter’ and you see oversized pulley systems marketed as ‘saves 2.4W’. If a given crankset was stiff enough to save 2.5W…it would be marketed as saving 2.5W.

Two things cyclists jump all over: ‘grams lighter’ and ‘watts saved’. If something isn’t marketed in those terms you may rest assured it’s because that thing does not provide those two advantages.

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